Joining is a process of connecting two or more components together either permanently or temporarily. Conventionally, the components are joined using thermal joining or mechanical joining techniques. Generally, thermal joining is used to form a permanent joint between components, and the mechanical joining may be used to join the components either permanently or temporarily. Fasteners like bolt and nut assembly, screws, pins, rivets and the like are used to mechanically join two or more members or structural components. Conventionally, a hole or a bore is machined through the components which are to be joined, and the fasteners are inserted through the hole or the bore to secure the components with one another. For example, when two plates abutting with each are to be held together, a hole or a bore is formed through depths of both the plates, and a fastener, like a pin or a rivet is inserted in the through-hole. However, when a bolt nut assembly is employed, the elongated portion of the bolt resides in the through-hole, and the nut is tightened on a free end of the elongated portion of the bolt. The nut so tightened will secure the abutting plates with each other. Further, the nature of joint between the components which are joined depends on the type of fastener used. A bolt and nut assembly may be regarded as a temporary fastening arrangement, since the nut can be unfastened to disassemble or separate one or more components from the rest.
Generally, a bolt includes a head portion and an elongated cylindrical body called a shank. The exterior of the shank may be provided with number of ridges called threads. On the other hand, a nut may have a central bore with internal threads, such that the threaded shank may reside and move inside the threaded bore of the nut. Either the stud or the nut is imparted with torque to fasten or unfasten. Fastening involves displacing the nut towards the head of the bolt so that the components to be fastened are secured to one another. While unfastening involves displacing the nut away from bolt head. Due to mechanical contact between the nut and the bolt, there are possibilities that with progress of time, the nut slowly starts unfastening from the bolt i.e. the nut gets displaced away from the bolt head. Various factors such as thermal expansion or contraction, vibrations, wear, warping, shrinkage, insufficient torque during fastening, etc., take part in self-unfastening of the nut relative to bolt. The phenomenon is referred to as “self-loosening”. The self-loosening phenomenon influenced by various factors mentioned above may lead to undesirable outcomes, such as separation of the heavy mechanical and structural components, leading to complications. One example of such a scenario includes sudden detachment of wheel from vehicle wheel hub, which is undesirable. In this case, the wheel rim containing the tyre may be fastened to the wheel hub, with the wheel hub containing plurality of bolts, and wheel rim containing nuts which can be fastened onto the bolts. When the vehicle propels, the wheel assembly comprising wheel rim and wheel hub is subjected to forces, torques and vibrations. These forces may eventually lead to self-loosening of one or more nuts from the bolts, consequently resulting in loosening of wheel rim from the hub. Another limitation is that in most of the cases, fastening is done manually i.e. the nut is fastened onto the bolt by applying torque manually using conventionally known tools, machine tools or devices. The manual fastening would not provide equal torsion between nuts and their respective bolts. With the progress of time, the nuts which were not torqued appropriately may undergo self-loosening, resulting in improper alignment between the components which are fastened. This in turn may result in transmission losses, reduction in transmission efficiency, deformations of mechanical members or even untimely failure of the components.
Several techniques have been implemented in the past to remedy self-loosening of the nut from the bolt, or vice-versa. One such technique utilizes a device which determines position of one component with respect to the other, for example, two or more flanges. The components are held together by a plurality of fasteners. The device is accommodated in one of the components. Whenever there is self-loosening between the fasteners, the device detects displacement of one component relative to adjacent component, and accordingly, the user may be alerted. The user, upon receiving the alert, may be prompted to manually fasten the nut relative to the bolt to secure the components. Another such fastening arrangement utilizes a fluid filled in a cavity inside the bolt. Whenever the nut is fully torqued with respect to bolt, the fluidic forces are sensed by sensors, and corresponding to the signals, user is alerted. The user may then manually torque the nut relative to the bolt for fastening. A limitation with the techniques described above may include lack of reliability since various mechanical factors are involved in determining the self-loosening. Also, a compromise is made in accuracy at which the self-loosening is determined.
The present disclosure is directed to address one or more problems as discussed above.